The invention relates to a plant for producing a metal band coated with at least one protection layer.
Generally, it is known that metal bands are realised in several successive steps, first of all the preparation of a raw product, by ingot mould casting or continuous casting, forging and hot-rolling of this product for providing a so-called xe2x80x98hotxe2x80x99 band reel and finally, cold rolling. Before cold rolling, the hot reel undergoes, generally, a descaling operation, for example, by etching or sandblasting. Cold rolling is realised, normally, in several successive steps, either into two opposite directions on a reversible train, or over several roll stands operating in tandem. An annealing treatment can also be necessary. On the other hand, cold transformation ends, most often, by a finishing treatment by passing, for example, through a xe2x80x98skin-passxe2x80x99 mill and a planer, to provide the requested surface quality and mechanical characteristics.
Moreover, for certain applications, the band must be coated with a protection layer which may be a metal coating realised, generally, by galvanisation or, more easily, a plain coating such as paint.
These different treatments are realised in specific pieces of equipment which, normally, operate at different speeds and it is the reason why they had been, previously, realised in separate sections of a factory or even in different factories, whereby the band is wound into a reel to be transported from one section to the next.
For some years, it has been sought to integrate as far as possible several successive treatments in a continuous production line in order to avoid load failures, intermediate storage or reel handling from one section to the next. For example, a modern plant may comprise, in a single line, an etching section, a tandem roll mill, an annealing furnace and a sizing stand.
However, the different sections, for example the annealing, etching and rolling sections, operate at rather different speeds and may be slowed down or even stopped in case of failure or, simply, for maintenance purposes. It is therefore necessary to interpose, between certain sections, accumulators that enable to proceed with the treatment in a section in the case of stoppage or slowing down of the band in a section placed upstream or to accumulate the band at the exit of a handling section in case the production has stopped downstream.
A plant of such type is described, for example, in an article entitled xe2x80x98Tomorrow""s cold factoryxe2x80x99 published in the Revue de Metallurgie, January 1990.
Until now, such plants, which call for considerable investments, were considered as profitable only for very large productions. They operate therefore at very high speeds and, in order to absorb a stoppage or a slowing down, even for a few minutes, over a treatment section, the accumulators must have a capacity of several hundred meters. Usually, the band forms a number of parallel belts following two-ways paths determined by a set of fixed rolls and a set of mobile rolls placed on a looping-in carriage movable between two positions, respectively a minimum accumulation position and a maximum accumulation position. However, such an accumulator remains very cumbersome and continuous line plants are therefore placed in very large buildings comprising one or several halls fitted with travelling cranes enabling to handle the reels and/or the parts necessary to the maintenance of the various pieces of equipment. Such buildings cover a very large ground surface and are very expensive.
As stated, after cold transformation and finishing treatments, the rolled band must often be coated, at least over one face, with a protection layer, for example a metal galvanisation coating or a paint.
It is known that for galvanisation, the metal band passes first of all through a liquid metal bath that is deposited, at exit, on each face of the band, while forming a metal layer whose thickness is adjusted by a rinsing means. To ensure regularity of the deposit, it is necessary that the band should run vertically when exiting from the bath. The metal deposited is then cooled down to solidification. Generally, the band runs therefore along a path comprising a rising vertical branch extending along a cooling device over sufficient length so that the metal can be solidified sufficiently to pass over a deflector roll and a falling branch along which the band is cooled further.
Such a plant is therefore placed in a building whose height corresponds to the necessary cooling length.
The coating can also be applied as the band is running between paint spraying means or rolls.
However, the customers"" requirements are quite varied and, according to the usage foreseen, it may prove necessary to provide for galvanisation or paint or even two superimposed protection layers.
After production, for example, of a number of reels of a galvanised band, the order book may call for the realisation of paint-coated band. To meet such requirements with great flexibility, a production factory, even if it is specialised in a certain type of product, must therefore comprise numerous pieces of equipment enabling to perform the necessary operations, for example, a cold rolling line with, possibly, annealing and etching, a galvanisation line and a paint-coating line.
Most often, these pieces of equipment are placed in separate buildings, whereas the cold rolled reels are directed to either of both coating lines in relation to the order book.
This enables to use pieces of equipment whose production can be suited to the needs, but handling the reels may damage the said reels and calls for intermediate storage steps.
Moreover, such a factory consisting of several buildings, which are used solely in relation to the needs, covers globally an extremely large surface.
Besides, it is sometimes necessary to apply a coat of paint over a metal coating whose surface quality must then be suited to the application of a paint.
It appears therefore that it would be interesting to combine the different treatments in order to meet the customers"" requirements easily, but this is difficult in current plants whose operating conditions are rather rigid.
The object of the invention is to remedy these different problems thanks to a multi-purpose plant enabling to regroup, in the same line, the pieces of equipment necessary to coatings of different types. Moreover, the invention enables to use these pieces of equipment, either individually or in combination with other pieces of equipment, for example to provide the necessary surface quality or to produce an additional coating.
The invention therefore relates to a plant for producing a metal band coated with at least one protection layer comprising means for controlling the running of the band, successively, through a series of treatment sections, placed one after the other in a continuous line. According to the invention, the plant comprises at least, in one running direction of the band:
a supply section,
a first metal-type coating section with two lateral sides perpendicular to a longitudinal running direction of the band, respectively a first side and a second side, and comprising a means for feeding the band into the said metal coating section, located at a low level of the first lateral side of the said section and ending in a tub liable to be filled with a liquid metal bath, means for guiding the band along a first running path comprising an immersion section penetrating into the tub for depositing metal on the band, a rising section extending along a more or less vertical direction between the exit from the tub and a high level and a falling section extending between the said high level and an exit means from the said first coating section, located at a low level on the second lateral side of the said section, and cooling means arranged at least along the rising section of the said first running path for solidification of the metal deposited on the band,
a second application-type coating section, located beside the first section and having two lateral sides perpendicular to the running direction, respectively a first side extending along the second side of the metal coating section and a second side, whereas the said coating section comprises means for coating the band, means that are placed at a low level of the said first side, means for guiding the band along a second running path passing in front of the said coating means and comprising at least one rising section extending vertically between the low level of the said coating means and a high level, means for drying the coating after application, extending at least along the said rising section and an exit means from the application section, placed on the second side thereof,
an exit section comprising at least one band accumulator and winding means.
Thanks to the invention, the whole plant can be placed in a single building comprising a central tower with two abutting sections in which are provided both coating sections, respectively metal-type and application-type coating sections, as well as two halls of smaller height that extend on either side of the said central tower and in which are installed, respectively, the supply section and the exit section.
Preferably, both these halls exhibit each a height and a length corresponding at least to the height and to the length of an accumulator with corresponding capacity.
In particular, the exit hall exhibits advantageously a height determined in order to cover an exit accumulator while leaving beneath the said accumulator a space of sufficient height to contain, on the one hand a complementary treatment section of the band extending beneath a rear portion of the accumulator and, on the other hand, at least means for winding the band extending beneath a front portion of the accumulator, whereas the length of the said hall is determined in order to leave, ahead of the accumulator, a space necessary to place a means for turning the band over and, possibly, inspection means.
The second hall in which the supply section is placed exhibits advantageously a height determined in order to cover the whole inlet accumulator and an annealing furnace that are superimposed.
The complementary treatment section that is placed on the path of the band between the exit from the first metal coating section and the inlet into the second application-type coating section, comprises for example a xe2x80x98skin-passxe2x80x99 mill, located between two tensioners and/or a loaded planer and/or an additional coating device such as a chromating or phosphating device.
According to a particularly advantageous embodiment, enabling to reduce the space requirements of the plant, the inlet means into the second application-type coating section is placed on the second side thereof, opposite to the first coating section and the band then follows, between both coating sections, a bent linking path comprising a first horizontal branch passing, at low level, beneath the second coating section, and on which can be placed a complementary treatment section, and a second horizontal branch returning, at middle level, to an inlet means into the second coating section.
According to another preferential characteristic, the plant comprises means for putting into service, selectively, each treatment section thereby enabling to choose an operating mode suited to the needs among a set of combination possibilities of the said treatment sections, for example a first mode with metal coating only, a second mode with metal coating and complementary treatment, a third mode with complementary treatment and application-type coating, a fourth mode with two combined coatings, respectively metal and application, as well as a complementary treatment comprising at least a xe2x80x98skin-passxe2x80x99 and a fifth mode with application-type coating only.
In order not to mark the band, at the exit from the painting line, it would be preferable to use a vertical accumulator but the latter should be placed in another tall building.
To remedy this shortcoming, a horizontal accumulator is used comprising, in a known fashion, a plurality of parallel belts travelling back and forth, between which are interposed separating arms spaced apart. However, according to another characteristic of the invention, the rear portion of the accumulator comprised between a middle position of the looping-in carriage and its retracted position for minimum accumulation, is deprived of separating arms, whereas tensioners are placed upstream and downstream the accumulator in order to maintain sufficient load on the band to avoid any contacts between the belts travelling back and forth. In such a case, only the rear portion of the accumulator, without any separating arms, is used in paint mode.